Field of the Invention
The present invention relates to a flexible display panel, and more particularly, to a flexible display panel for suppressing a problem in which a crack such as disconnection on an internal circuit layer or the like is generated or a required warpage level is not attainable in a warped area while bending an edge portion thereof.
Description of the Related Art
In recent years, while interest in information displays has risen and demand for using portable information media has increased, studies on flat panel display devices (FPDs) for replacing the existing display devices such as cathode ray tubes and commercialization thereof have been mostly carried out.
In such a flat panel display field, though liquid lightweight and low-power liquid crystal display devices have been most noteworthy flat panel display devices up to now, development on new flat panel displays has been actively carried out according to various requirements.
Since organic light emitting diode (OLED) display devices, which are one of new flat panel displays, are a spontaneous light-emitting type, they have excellent viewing angle and contrast range characteristics but do not require a backlight contrary to liquid crystal displays, and thus allowing a lightweight and low profile device as well as being beneficial in the aspect of power consumption. Furthermore, they have an advantage in low DC voltage drive and high response speed, and also particularly have a beneficial advantage in the aspect of fabrication cost.
In particular, flexible display devices, which are not likely to be damaged even when folded or rolled up, will be emerged as a new technology in the flat panel display device field, and organic light emitting display devices in which pixel formation is easily made on a flexible plastic substrate are more suitable than liquid crystal displays, mostly using a glass substrate, in implementing a flexible display device with the development of technology.
FIG. 1 is a view schematically illustrating a flexible display panel with a plastic material substrate used in a flexible display device according to the related art.
Referring to FIG. 1, a flexible display device 1 is formed with an active area (A/A) in which an actual image is implemented on a plastic substrate 10 and a non-active area (N/A) surrounding the active area (A/A). Though not shown in the drawing, a pixel area defined by a plurality of gate lines and data lines is formed in the active area (A/A), a plurality of thin film transistor are formed in the pixel area.
Furthermore, two gate driving circuits 30 are embedded therein in a gate-in-panel (GIP) structure at the left and right side ends of the non-active area (N/A) of the flexible display device 1. The gate driving circuit 30 supplies a gate signal to each pixel through a signal line connected to a gate line in the active area (A/A). Furthermore, a data driving circuit 40 connected to a data line on the active area (A/A) is provided at one side of the non-active area (N/A). The data driving circuit 40 is electrically connected to a pad 46 formed at one side end of the flexible display panel 1. In addition, a polarizing film 60 for compensating the optical characteristics of the flexible display panel 1 is adhered onto a front surface of the active area (A/A).
In implementing a display device using a flexible display panel with the foregoing structure, there is proposed a structure in which a narrow bezel is implemented by bending at least one side end thereof.
FIG. 2 is a view for explaining the bending structure of a narrow bezel structured flexible display panel according to the related art.
Referring to FIG. 2, the flexible display device 1 defined by an active area (A/A) formed with a plurality of pixels and a non-active area (N/A) surrounding the active area (A/A) is configured with a form in which a plastic substrate 10 configured with a polyimide or the like, a driving element layer 20 including various signal lines and a plurality of thin film transistors formed on the substrate 10, a light-emitting element layer 25 formed on the driving element layer 20 to implement an image, a barrier film 40 configured to protect the driving element layer 20 and light-emitting element layer 25 thereunder, and a polarizing film 60 configured to compensate optical characteristics are layered thereon. Furthermore, a supporting film 70 with a polyethylene terephthalate (PET) material for supporting the flexible display panel 1 is further adhered to a lower portion of the substrate 10. Here, the non-active area (N/A) is not an area for displaying an image, and thus is configured not to include the light-emitting element layer 25, barrier film 40, and polarizing film 60, but configured to include a predetermined signal line and thin film transistor constituting a gate driving circuit in a GIP manner.
In order to implement a narrow bezel in a flexible display device with the foregoing structure, it is configured such that the non-active area (N/A) is warped in the rear surface direction of the display panel 1. Here, metals constituting the signal lines and thin film transistors contained in the driving element layer 20 are formed of titanium/aluminum/titanium (Ti/Al/Ti) in case of source/drain electrodes, and formed of molybdenum niobium/aluminum (MoNb/Al) in case of a gate electrode, and a crack is often generated according to a force acting on the driving element layer 20 during the bending process.
Furthermore, the supporting film 70 adhered to a lower portion of the plastic substrate 10 has a characteristic of not being easily warped compared to the plastic substrate 10, thereby causing a problem in which the bending structure cannot be maintained as it is during the module process of the display device.